ES2704270T3 - Guard interval indication for the determination of the number of data symbols - Google Patents

Abstract

A method for wireless communications, comprising: receiving, by a user terminal (120), a data packet comprising one or more data symbols; extracting, by the user terminal (120), a length field, LENGTH, and a correction field from the data packet, and calculating, by the user terminal (120), a number of data symbols, Nsym, in the packet, based on the length field using one of the expressions: NSYM = ceil((LENGTH+3) / 3) - 4 - NVHT-LTF; NSYM = ground((ceil((LENGTH+3)/3)-4-NVHT-LTF)*4/3.6); and NSYM = ground((ceil((LENGTH+3)/3) - 4 - NVHT-LTF) *4/3.6) - 1, where NVHT-LTF is the number of Very High Long Learning Fields Performance and in which the expression is chosen based on the correction field.

Description

DESCRIPTION

Guard interval indication for the determination of the number of data symbols

CROSS REFERENCE TO RELATED REQUESTS

[0001] This application claims the priority of U.S. Provisional Patent Application Serial No. 61 / 378,642, entitled "SIGNAL OF GUARD INTERVAL FOR DETERMINATION OF THE NUMBER OF DATA SYMBOLS"['GUARO INTERVAL SIGNALING FOR DATA SYMBOL NUMBER DETERMINATION '], filed on August 31, 2010.

BACKGROUND

Field

[0002] Certain aspects of the present disclosure generally relate to wireless communications and, more particularly, to techniques for accurately determining various data symbols in a data packet.

Background

[0003] To deal with the problem related to the increasing bandwidth requirements demanded by wireless communication systems, different schemes are being developed that allow multiple user terminals to communicate with a single access point by sharing the resources of channel, obtaining at the same time high data flows. Multiple input and multiple output (MIMO) technology represents such an approach, which has recently emerged as a popular technique for next-generation communications systems. MIMO technology has been adopted in several emerging wireless communications standards, such as the standard of the Institute of Electrical and Electronic Engineers (IEEE) 802.11. The IEEE 802.11 standard indicates a set of wireless local area network (WLAN) air interface standards developed by the IEEE 802.11 committee for short-range communications (for example, between tens and a few hundred meters).

[0004] A MIMO system employs multiple (N ^t ) transmit antennas and multiple (N ^r ) receive antennas for data transmission. A MIMO channel formed by the N ^T transmit antennas and N ^r receive antennas may be decomposed into N ^s independent channels, which are also called spatial channels, where N ^s to min (N ^t, N ^r}. Each N ^s independent channels corresponds to a dimension. the MIMO system can provide improved performance (e.g., increased traffic throughput and / or greater reliability) if the additional dimensions created by the multiple transmit antennas and reception are used.

[0005] In wireless networks with a single Access Point (AP) and multiple user stations (STA), concurrent transmissions may occur on multiple channels to different stations, both in the uplink and downlink direction. Such systems present many challenges.

[0006] Youhan Kim ET AL document: " VHT Packet Duration Signaling", Date: 07-12-2010 discloses a procedure for calculating the number of data symbols by a user based on a length field and a correction field in the preamble of a data packet.

SUMMARY

[0007] The main aspects of the present disclosure are provided in the independent claims 1,4, 7. Advantageous embodiments are described in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Therefore, to understand in detail the aforementioned characteristics of the present disclosure, a more particular description is offered, briefly summarized above, with reference to its aspects, some of which are illustrated in the attached drawings. However, it should be noted that the attached drawings only illustrate certain typical aspects of this disclosure and, therefore, should not be considered as limiting its scope, since the description may admit other equally effective aspects.

FIG. 1 illustrates a diagram of a wireless communications network in accordance with certain aspects of the present disclosure.

FIG. 2 illustrates a block diagram of an example of access point and user terminals according to certain aspects of the present disclosure.

FIG. 3 illustrates a block diagram of an example wireless device according to certain aspects of the present disclosure.

FIG. 4 illustrates an exemplary structure of the preamble transmitted from an access point in accordance with certain aspects of the present disclosure.

FIG. 5 illustrates exemplary operations that can be performed at an access point (AP) to provide a correction factor for an ambiguous length field, according to certain aspects of the present disclosure.

FIG. 5A illustrates exemplary means capable of carrying out the operations shown in FIG. 5.

FIG. 6 illustrates exemplary operations that can be performed in a user terminal to correct a number of data symbols calculated based on an ambiguous length field, in accordance with certain aspects of the present disclosure.

FIG. 6A illustrates exemplary means capable of carrying out the operations shown in FIG. 6

FIG. 7 illustrates an example of an ambiguous length field that can be corrected, in accordance with certain aspects of the present disclosure.

FIG. 8 illustrates an example of a correction field that can be provided to correct a number of data symbols calculated based on an ambiguous length field, in accordance with certain aspects of the present disclosure.

DETAILED DESCRIPTION

[0009] The aspects of the present disclosure provide techniques that can be used to help resolve ambiguities in a length field of a data packet. Ambiguities can arise when data symbols use short guard intervals (GI). Data symbols with these short GIs have a transmission time that is less than a resolution of a length field provided in the data packet, which can result in the same value of the length field that is calculated for different numbers of symbols. The techniques provided herein may allow a receiving terminal to correct several symbol calculations based on such ambiguous length field values.

[0010] Various aspects of the disclosure are described below in greater detail with reference to the accompanying drawings. However, this disclosure can be made in many different ways and should not be considered to be limited to any specific structure or function presented throughout this disclosure. Instead, these aspects are provided so that this disclosure is thorough and complete, fully conveying the scope of the disclosure to those skilled in the art. Based on the teachings herein, those skilled in the art will appreciate that the scope of the disclosure is intended to cover any aspect of the disclosure disclosed herein, whether implemented independently of or in combination with any other aspect of the disclosure. divulgation. For example, an apparatus may be implemented or a method may be implemented using any number of aspects disclosed herein. In addition, the scope of the disclosure is intended to cover an apparatus or method of this type implemented using another structure, functionality, or structure and functionality, in addition to or different from the various aspects of the disclosure described herein. It should be understood that any aspect of the disclosure disclosed herein may be accomplished by one or more elements of a claim.

[0011] The term "example" is used herein in the sense of "serving as an example, instance or illustration". It should not be considered that any aspect described herein as "exemplary" is preferred or advantageous with respect to other aspects.

[0012] Although particular aspects are described herein, many variations and permutations of these aspects are within the scope of the disclosure. Although some benefits and advantages of the preferred aspects are mentioned, the scope of the disclosure is not intended to be limited to particular benefits, uses or objectives. In contrast, the aspects of the disclosure can be applied, generally, to different wireless technologies, system configurations, networks and transmission protocols, some of which are illustrated by way of example in the figures and in the following description of the preferred aspects. The detailed description and the drawings merely illustrate the disclosure and do not limit the scope of the disclosure, which is defined by the appended claims.

A SYSTEM OF WIRELESS COMMUNICATIONS OF EXAMPLE

[0013] The techniques described herein can be used in various wireless broadband communication systems, including communication systems that are based on an orthogonal multiplexing scheme. Examples of such communication systems include multiple access systems by spatial division (SDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access systems (SC-FDMA), etc. An SDMA system can use sufficiently different addresses to simultaneously transmit data belonging to multiple user terminals. A TDMA system may allow multiple user terminals to share the same frequency channel by dividing the transmission signal into different time slots, each time slot being assigned to different user terminals. An OFDMA system uses orthogonal frequency division multiplexing (OFDM), which is a modulation technique that divides the global system bandwidth into multiple orthogonal subcarriers. These subcarriers can also be called shades, containers, etc. With OFDM, each subcarrier can be modulated independently with data. An SC-FDMA system can use interlaced FDMA (IFDMA) to transmit on subcarriers that are distributed across the system bandwidth, localized FDMA (LFDMA) to transmit on a block of adjacent subcarriers, or enhanced FDMA (EFDMA) to transmit in multiple blocks of adjacent subcarriers. In general, the modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDMA.

[0014] The teachings of the present document can be incorporated into (eg, implemented in or carried out by) various wired or wireless devices (e.g., nodes). In some aspects, a wireless node implemented according to the teachings of this document may comprise an access point or an access terminal.

[0015] An access point ("AP") may comprise, be implemented as or be known as a NodeB, a Radio Network Controller ("RNC"), an eNodeB, a Base Station Controller ("BSC"), a Base Transceiver Station ("BTS"), a Base Station ("BS"), a Transceiver Function ("TF"), a Radio Router, a Radio Transceiver, a Basic Service Set ("BSS"), a Set of Extended Services ("ESS"), a Radio Base Station ("RBS"), or using other terminology.

[0016] An access terminal ("AT") may comprise, be implemented as or be known as an access terminal, a subscriber station, a subscriber unit, a mobile station, a remote station, a remote terminal, a terminal user, a user agent, a user device, a user equipment, a user station or using other terminology. In some implementations, an access terminal may comprise a cellular telephone, a cordless telephone, a session initiation protocol ("SIP") telephone, a wireless local loop ("WLL") station, a personal digital assistant ( "PDA"), a handheld device with wireless connection capability, a station ("STA") or some other suitable processing device connected to a wireless modem. Accordingly, one or more aspects disclosed herein may be incorporated into a telephone (e.g., a cellular phone or smartphone), a computer (e.g., a portable computer), a portable communications device, a device portable computer (for example, a personal data assistant), an entertainment device (for example, a music or video device, or a satellite radio), a global positioning system device or any other suitable device that is configured to communicate through a wireless or wired means. In some aspects, the node is a wireless node. This wireless node can provide, for example, connectivity to a network (e.g., a wide area network such as the Internet or a cellular network) through a wired or wireless communication link.

[0017] FIG. 1 illustrates a system of multiple accesses of multiple entrances and multiple exits (MIMO) 100 with access points and user terminals. For the sake of simplicity, only one access point 110 is shown in Figure 1. An access point is generally a fixed station that communicates with the user terminals and may also be referred to as a base station or other terminology. A user terminal may be fixed or mobile, and may also be referred to as a mobile station, a wireless device, or some other terminology. The access point 110 may communicate with one or more user terminals 120 at any given time in the downlink and the uplink. The downlink (that is, the direct link) is the communication link of the access point to the user terminals, and the uplink (that is, the reverse link) is the communication link from the user terminals to the point of access. A user terminal may also communicate between peers with another user terminal. A system controller 130 is coupled to and provides coordination and control for the access points.

[0018] Although portions of the following disclosure will describe user terminals 120 capable of communicating through space division multiple access (SDMA), for certain aspects, user terminals 120 may also include some user terminals that do not support SDMA. Therefore, for such aspects, an AP 110 can be configured to communicate with both SDMA and non-SDMA user terminals. This approach can conveniently allow previous versions of user terminals ("legacy" stations) to remain in place in a company, extending their useful life, also allowing the introduction of new SDMA user terminals as deemed appropriate.

[0019] The system 100 employs multi-transmit and multiple-receive antennas for data transmission in the downlink and the uplink. The access point 110 is equipped with N ^ap antennas and represents the multiple input (MI) for downlink transmissions and the multiple output (MO) for the uplink transmissions. A set of K user terminals 120 selected together represents the multiple output for downlink transmissions and the multiple input for uplink transmissions.

For a pure SDMA, it is desired to have N ^ap >K> 1 if the data symbol streams for the K user terminals are not multiplexed in code, frequency or time by some means. K may be greater than N ^ap if the data symbol streams can be multiplexed using TDMA technique, different code channels with CDMA, discontinuity sets of sub-bands with OFDM, etc. Each selected user terminal transmits user-specific data and / or receives user-specific data from the access point. In general, each selected user terminal may be equipped with one or multiple antennas (ie, N ^ut > 1). The selected user terminals K may have the same or different number of antennas.

[0020] The MIMO system 100 can be a time division duplex (TDD) system or a frequency division duplex (FDD) system. For a TDD system, the downlink and the uplink share the same frequency band. For an FDD system, the downlink and the uplink use different frequency bands. The MIMO 100 system can also use a single carrier or multiple carriers for transmission. Each user terminal is equipped with a single antenna (for example, to keep the cost down) or multiple antennas (for example, when the additional cost can be assumed). The system 100 can also be a TDMA system if the user terminals 120 share the same frequency channel by dividing the transmission / reception in different time slots, each time slot being assigned to a different user terminal 120.

[0021] FIG. 2 illustrates a block diagram of the access point 110 and two user terminals 120m and 120x in the MIMO system 100. The access point 110 is equipped with N ^t antennas 224a to 224t. The user terminal 120m is equipped with N ^{ut, m} antennas 252ma to 252mu, and the user terminal 120x is equipped with Nut, x antennas 252xa to 252xu. The access point 110 is a transmission entity for the downlink and a receiving entity for the uplink. Each user terminal 120 is a transmit entity for the uplink and a receive entity for the downlink. As used herein, a "transmitting entity" is a stand-alone device or device capable of transmitting data over a wireless channel, and a "receiving entity" is an autonomous device or device capable of receiving data. through a wireless channel. In the following description, the subscript "dn" represents the downlink, the subscript "up" represents the uplink, select N ^up user terminals for a simultaneous transmission in the uplink, select N ^dn user terminals for a simultaneous transmission in the downlink, N ^up can be equal or not to N ^dn , and N ^up and N ^dn can be static values or can change for each planning interval. The beam orientation or some other spatial processing technique can be used at the access point and the user terminal.

[0022] In the uplink, at each user terminal 120 selected for uplink transmission, a TX data processor 288 receives traffic data from a data source 286 and control data from a controller 280. The processor TX data 288 processes (eg, encodes, interleaves and modulates) the traffic data for the user terminal based on the coding and modulation schemes associated with the selected speed for the user terminal and provides a data symbol stream . A spatial processor TX 290 performs spatial processing in the data symbol stream and provides N ^{ut, m} streams of transmission symbols for N ^{ut, m} antennas. Each transmission unit (TMTR) 254 receives and processes (for example, converts to analog, amplifies, filters and converts frequency upwards) a respective transmission symbol stream to generate an uplink signal. N ^{ut, m} transmission units 254 provide N ^{ut.m uplink} signals for transmission from N ^{ut, m} antennas 252 to the access point.

[0023] N ^up user terminals can be scheduled for simultaneous transmission in the uplink. Each of these user terminals performs spatial processing in its data symbol flow and transmits its set of transmission symbol flows in the uplink to the access point.

[0024] In the access point 110, N ^ap antennas 224a to 224ap receive the uplink signals from all N ^up user terminals transmitting on the uplink. Each antenna 224 provides a received signal to a respective reception unit (RCVR) 222. Each receiving unit 222 performs processing complementary to that performed by the transmission unit 254 and provides a stream of received symbols. A spatial processor RX 240 performs spatial processing of reception on the N ^ap symbol streams received from the N ^ap receiving units 222 and provides N ^up uplink data symbols recovered. The reception spatial processing is carried out according to the channel correlation matrix inversion (CCMI), the minimum mean square error (MMSE), a successive interference cancellation (SIC) or with some other technique. Each recovered uplink data symbol stream is an estimate of a data symbol stream transmitted by a respective user terminal. An RX data processor 242 processes (e.g., demodulates, deinterleaves and decodes) each uplink data symbol stream retrieved according to the rate used by that stream to obtain decoded data. The decoded data for each user terminal can be provided to a data collector 244 for storage and / or to a controller 230 for further processing.

[0025] In the downlink, at the access point 110, a TX data processor 210 receives traffic data from a data source 208 for N ^dn user terminals scheduled for downlink transmission, control data from a controller 230 and, possibly, other data from a 234 scheduler. Various types of data can be sent in different transport channels. The TX data processor 210 processes (e.g., encodes, interleaves and modulates) the traffic data for each user terminal based on the speed selected for that user terminal. The data processor TX 210 provides N ^dn downlink data symbol streams for the N ^dn user terminals. A spatial processor TX 220 performs spatial processing (such as a precoding or a beam shaping, as described in the present disclosure) in the downlink data symbol flows Ndn and provides N ^ap streams of transmission symbols for the N ^ap antenas. Each transmit unit 222 receives and processes a stream of respective transmission symbols to generate a downlink signal. N ^ap transmitter units 222 provide N ^ap downlink signals for transmission from N ^ap antennas 224 to the user terminals.

[0026] At each user terminal 120, N ^{ut, m} antennas 252 receive the N ^ap downlink signals from the access point 110. Each receiving unit 254 processes a received signal from an associated antenna 252 and provides a flow of received symbols. A spatial processor RX 260 performs a reception spatial processing on the N ^{ut, m} symbol streams received from N ^{ut, m} receiving units 254 and provides a downlink data symbol stream retrieved for the user terminal. The reception spatial processing is carried out according to the CCMI, the MMSE or some other technique. An RX data processor 270 processes (e.g., demodulates, de-interlaces and decodes) the recovered downlink data symbol stream to obtain decoded data for the user terminal.

[0027] At each user terminal 120, a channel estimator 278 estimates the downlink channel response and provides downlink channel estimates, which may include channel gain estimates, SNR estimates, noise variance, etc. . Also, a channel estimator 228 estimates the uplink channel response and provides uplink channel estimates. The controller 280 for each user terminal normally obtains the spatial filter matrix for the user terminal based on the downlink channel response matrix H ^{dn, m} for that user terminal. The controller 230 obtains the spatial filter matrix for the access point based on the effective uplink channel response matrix H ^up.eff . The controller 280 for each user terminal may send response information (e.g., eigenvectors, eigenvalues, SNR estimates, downlink and / or uplink) to the access point. The controllers 230 and 280 further control the operation of several processing units at the access point 110 and the user terminal 120, respectively.

[0028] FIG. 3 illustrates various components that can be used in a wireless device 302 that can be employed in a wireless communication system, such as the MIMO system 100. The wireless device 302 is an example of a device that can be configured to implement the various procedures described in present document. The wireless device 302 can be an access point 110 or a user terminal 120.

[0029] The wireless device 302 may include a processor 304 that controls the operation of the wireless device 302. The processor 304 may also be referred to as the central processing unit (CPU). The memory 306, which may include both read-only memory (ROM) and random access memory (RAM), provides instructions and data to the processor 304. A portion of the memory 306 may also include a non-volatile random access memory (NVRAM). ). The processor 304 typically performs logical and arithmetic operations based on program instructions stored in the memory 306. The instructions in the memory 306 may be executed to implement the methods described herein.

[0030] The wireless device 302 may also include a housing 308 which may include a transmitter 310 and a receiver 312 to allow transmission and reception of data between the wireless device 302 and a remote location. Transmitter 310 and receiver 312 may be combined in a transceiver 314. A single or plurality of transmit antennas 316 may be attached to housing 308 and electrically coupled to transceiver 314. Wireless device 302 may also include (not shown) multiple transmitters , multiple receivers and multiple transceivers.

[0031] The wireless device 302 may also include a signal detector 318 that can be used to detect and quantify the level of signals received by the transceiver 314. The signal detector 318 can detect said signals as the total energy, energy per subcarrier per symbol, power spectral density and other signals. The wireless device 302 may also include a digital signal processor (DSP) 320 for use in signal processing.

[0032] The various components of the wireless device 302 may be coupled together via a bus system 322, which may include a power bus, a control signal bus, and a status signal bus in addition to a data bus.

[0033] FIG. 4 illustrates an exemplary structure of a preamble 400 in accordance with certain aspects of the present disclosure. The preamble 400 can be transmitted, for example, from the access point (AP) 110 to the user terminals 120 in the MIMO system 100 illustrated in FIG. one.

[0034] The preamble 400 may comprise an omni-inherited portion 402 (ie, the non-conformed portion). per beams) and a pre-coded IEEE 802.11ac VHT (very high performance) portion. The inherited portion 402 may comprise: an inherited short learning field (L-STF) 406, an inherited long learning field 408, a signal field inherited (L-SIG) 410, and two OFDM symbols for the VHT fields of signal A (VHT-SIG-A) 412, 414. The fields VHT-SIG-A 412, 414 (ie, VHT-SIG-A1 and VHT-SIG-A2) can be transmitted omnidirectionally and can indicate the assignment of spatial flow numbers to a combination (set) of STAs.

[0035] The pre-coded IEEE 802.11ac VHT portion 404 may comprise a short learning field VHT (VHT-STF) 418, a long learning field VHT 1 (VHT-LTF1) 420, long learning fields VHT (VHT-LTF) 422, a signal VHT field B (VHT-SIG-B) 424, and a data portion 426. The VHT-SIG-B field may comprise an OFDM symbol and may be transmitted precoded / preformed by beams.

[0036] A strong MU-MIMO reception may involve the AP transmitting all VHT-LTF 422 to all STAs. The VHT-LTF 422 may allow each STA to estimate a MIMO channel from all the AP antennas to the STA antennas. The STA can use the estimated channel to perform an effective interference nullity of the MU-MIMO flows corresponding to other STAs. To perform a strong interference cancellation, one can expect each STA to know what spatial flow belongs to that STA, and what spatial flows belong to other users.

SIGNALING OF INTERVAL OF GUARD FOR THE DETERMINATION OF THE NUMBER OF DATA SYMBOLS

[0037] The L-SIG field 410 may have a length field, that is, it indicates a packet duration as a whole number of symbols. For example, the length field L-SIG can indicate a packet duration as an integer of 4 us symbols. A receiving station can use the L-SIG length field to determine the number of data symbols in a packet, according to an equation described in more detail below.

[0038] In general, 802.11ac packets do not have a byte length field in VHT-SIG-A. Instead, the L-SIG LENGTH field contains a duration as in Mixed Mode 802.11 n, which provides the packet duration as an integer number of 4 microseconds (corresponding to 802.11a symbols). As a result, if you use a short guard interval, you can make an ambiguity in the L-SIG LENGTH.

[0039] For example, different packages with x and x-1 symbols, can both have the same L-SIG LENGTH. However, this ambiguity can only exist for several symbols of short guard intervals equal to 10n or 10n-1 where n is an integer. The ambiguity is due to the nature of the equation used to calculate the L-SIG LENGTH field, which includes a roof function. As will be described in more detail below, for a data packet with 1 VHT-LTF, the data packets with 20 and 19 short GI symbols have the same value of L-SIG LENGTH.

[0040] However, as described above, ambiguities may arise when the data symbols use short guard intervals (GI) with transmission times of less than 4 us, such as short GI symbols with transmission times of 3, 6 us. Since, in this case, data packets with different symbol numbers (N ^sym ) can be transmitted with the same Length value, a receiving entity can determine an incorrect number of data symbols.

[0041] According to certain aspects, in order to allow a receiving entity to resolve this ambiguity, a transmission entity can transmit a field indicating a length of the GI used for the data symbols and / or it can also indicate whether a number of symbols calculated based on a field of ambiguous length must be corrected or not.

[0042] As illustrated in FIG. 4, this field can be transmitted in the form of a multi-bit GI field 428. The GI field 428 can be included in the Vh T-SIG-A field 412. As will be described in more detail below, the field's multi-bit code GI 428 can indicate whether a long or short GI field is used in the data symbols and, in the case of data symbols with short GI, the GI field can also indicate whether the number of symbols calculated based on the length field should correct or not.

[0043] FIG. 5 illustrates exemplary operations that may be performed at an access point (AP) to generate and provide a correction factor for an ambiguous length field, in accordance with certain aspects of the present disclosure.

[0044] Operations 500 begin, at 502, generating a data packet comprising one or more data symbols. At 504, the AP provides, in a preamble field of the data packet, a length field which can be used to calculate a number of symbols by a receiving entity, as well as an indication of whether the calculated number of symbols should be corrected or do not. At 506, the AP can transmit the data packet and a receiving entity can calculate a number of data symbols based on the Length field and the indication.

[0045] FIG. 6 illustrates exemplary operations 600 that may be performed, for example, at a user terminal to correct a number of data symbols calculated based on an ambiguous length field, in accordance with certain aspects of the present disclosure.

[0046] The operations begin, at 602, by receiving a data packet comprising one or more data symbols. At 604, the UT extracts a length field and a correction field from the data packet. At 606, the UT calculates a number of data symbols in the packet, based on the length field and the correction field.

[0047] FIG. 7 shows a table 700 of Length values for various package configurations. The values illustrate the example, alluded to above, of an ambiguous length field value for data packets with 20 and 19 short GI symbols.

[0048] The values in table 700 assume a data packet with 1 VHT-LTF. As shown for long GI symbols, there is no ambiguity since each different number of symbols (N ^sym ), results in a different L-SIG LENGTH value. On the other hand, for short GI symbols, data packets with 20 and 19 short GI symbols have the same value of L-SIG LENGTH.

[0049] The reason for the ambiguity can be observed by examining the equation used to calculate the length value:

LENGTH = ceil ((TXTIME-20) / 4) x 3 - 3 (1)

where

TXTIME = 36 + 4N ^vht - ^ltf + N ^sym T (2)

where T is 4 or 3.6 microseconds depending on the guard interval (4 for long, 3.6 for short), N ^sym is the number of DATA symbols (does not include VHT-SIG-B), and 36 + 4N ^vht - ^ltf is the duration of the preamble in microseconds. This can include VHT-SIG-B that always uses a long guard interval.

[0050] In the equation for LENGTH L-SIG, above, "ceil" is the ceiling function. Since "ceil (x)" is defined as "the smallest integer not less than x". Since the argument of the ceiling function in the above equation has a divisor of 4 and, for short GI symbols, TXTIMEs for consecutive NSYM values will differ by less than four, the roof function argument will differ by less than one. Therefore, in the case that the argument does not result in different values of integers, the values of LENGTH L-SIG will be the same, as with N ^sym = 19 and 20.

[0051] FIG. 8 illustrates exemplary values for a GI correction field that can be provided to correct a number of data symbols calculated based on an ambiguous length field, in accordance with certain aspects of the present disclosure. As discussed above, aspects of the present disclosure can help resolve this ambiguity by making the GI field that has been described above dependent on the number of data symbols and, on the receiver side, corresponding different equations can be used to calculate N ^sym , with the equation selected based on the GI bit values. Although not shown, the value "b01" can be a reserved value.

[0052] Although the equation LENGTH (1) above can be used most of the time, if a short GI is used and the number of symbols modulo 10 is 9 (N ^sym % 10 = 9), different equations can be used, to calculate N ^sym . For example, for GI = b00, the following equation can be used (based on the previous EC (1)):

N ^sym = ceil ((LENGTH + 3) / 3) - 4 - N ^vht - ^ltf (3)

for b10:

N ^sym = soil ((ceil ((LENGTH + 3) / 3) - 4 - N ^vht - ^ltf ) * 4 / 3.6) (4)

and for b'11 '

N ^sym = soil ((ceil ((LENGTH + 3) / 3) - 4 - N ^vht - ^ltf ) * 4 / 3,6) - 1 (5)

Therefore, even if an ambiguous LONGITUDE value is transmitted, ambiguity can be solved by using the correct N ^sym equation based on the GI field.

[0053] The various procedural operations described above can be carried out by any suitable means that can carry out the corresponding functions. The means may include various components and / or hardware and / or software modules including, but not limited to, a circuit, an integrated circuit of specific application (ASIC) or a processor. Generally, if the figures illustrate operations, those operations may have corresponding homologous means and function components with a similar numbering. For example, operations 500 and 600 illustrated in FIGS. 5 and 6 correspond to the means 500A and 600A illustrated in FIGS. 5A and 6A.

[0054] For example, the transmission means may comprise a transmitter (e.g., the transmitter unit 222) and / or an antenna 224 of the access point 110 illustrated in FIG. 2. The receiving means may comprise a receiver (e.g., receiver unit 254) and / or antenna 252 of user terminal 120 illustrated in FIG. 2. The processing means, the means of determination or the means of use may comprise a processing system, which may include one or more processors, such as the RX 270 data processor, the TX data processor 288 and / or the controller 280 of user terminal 120 illustrated in FIG.

two.

[0055] As used herein, the term "determine" encompasses a large number of actions. For example, "determining" can include calculating, computing, processing, obtaining, researching, consulting (for example, consulting a table, a database or other data structure), finding out, etc. "Determine" can also include receiving (for example, receiving information), accessing (for example, accessing data from a memory), etc. "Determine" can also include solve, select, choose, set, etc.

[0056] As used herein, an expression referring to "at least one of" a list of elements refers to any combination of such elements, including individual elements. As an example, "at least one of: a, b oc" is intended to include: a, b, c, ab, ac, bc and abc.

[0057] The various illustrative logic blocks, modules and circuits described in connection with the present disclosure can be implemented or implemented with a general-purpose processor, with a digital signal processor (DSP), with a specific application integrated circuit (ASIC) , with a programmable field gate array (FPGA) or with another programmable logic device (PLD), transistor or discrete gate logic, discrete hardware components, or with any combination thereof designed to perform the functions described in This document. A general purpose processor may be a microprocessor but, alternatively, the processor may be any processor, controller, microcontroller or state machine available in the market. A processor can also be implemented as a combination of computing devices, for example a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors together with a DSP core or any other configuration of this type.

[0058] The steps of a method or algorithm described in connection with the present disclosure can be performed directly on hardware, on a software module executed by a processor or on a combination of the two. A software module may reside in any form of storage medium known in the art. Some examples of storage media that can be used include random access memory (RAM), read-only memory (ROM), flash memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, etc. A software module may comprise a single instruction or many instructions, and may be distributed in several different code segments, between different programs and among multiple storage media. A storage medium may be coupled to the processor so that the processor can read information from, and write information to, the storage medium. As an alternative, the storage medium can be an integral part of the processor.

[0059] The methods disclosed herein comprise one or more steps or actions to carry out the described procedure. The steps of the procedure and / or actions can be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is indicated, the order and / or use of specific steps and / or actions can be modified without departing from the scope of the claims.

[0060] The functions described can be implemented in hardware, software, firmware or any combination of the above. If implemented in hardware, an example hardware configuration may comprise a processing system in a wireless node. The processing system can be implemented with a bus architecture. The bus can include any number of interconnection buses and bridges depending on the specific application of the processing system and the overall design limitations. The bus can connect several circuits together, including a processor, machine-readable media and a bus interface. The bus interface can be used to connect a network adapter, among other things, to the processing system via the bus. The network adapter can be used to implement the signal processing functions of the PHY layer. In the case of a user terminal 120 (see Fig. 1), a user interface (e.g., a keyboard, a display device, a mouse, a control lever, etc.) can also be connected to the bus. The bus can also connect various other circuits such as timing sources, peripherals, voltage regulators, power management circuits, etc., well known in the art and, therefore, not described in greater detail.

[0061] The processor can take care of managing the bus and general processing, including running software stored on machine-readable media. The processor can be implemented with one or more processors of general purpose and / or special purpose. Examples include microprocessors, microcontrollers, DSP processors and other circuit systems that can run software. The term 'software' must be interpreted generically as instructions, data or any combination thereof, regardless of whether it is referred to as software, firmware, middleware, microcode, hardware description language or otherwise. The machine-readable media may include, by way of example, RAM (random access memory), flash memory, ROM (read-only memory), PROM (programmable read-only memory), EPROM (programmable read-only and erasable memory). ), EEPROM (electrically erasable, programmable read only memory), registers, magnetic disks, optical disks, hard drives or any other suitable storage media, or any combination thereof. Machine readable media can be made in a computer program product. The computer program product may comprise packaging materials.

[0062] In a hardware implementation, machine-readable media can be part of the processing system in addition to the processor. However, as will be readily appreciated by those skilled in the art, machine-readable media, or any part thereof, may be external to the processing system. By way of example, machine-readable media may include a transmission line, a data-modulated carrier wave and / or a computer product other than the wireless node, where the processor can access all of them via the bus interface. Alternatively, or additionally, the machine-readable media, or any part thereof, may be integrated into the processor, such as may be the case with the general cache and / or register files.

[0063] The processing system can be configured as a general purpose processing system, where one or more microprocessors provide the processor functionality and an external memory provides at least a part of the machine readable media, all of which are connected to another system of support circuits through an external bus architecture. As an alternative, the processing system can be implemented with an ASIC (specific application integrated circuit), with the processor, the bus interface, the user interface in the case of an access terminal, the support circuit system and the less a part of the machine-readable media integrated into a single chip, or with one or more FPGA (programmable field gate arrays), PLD (programmable logic devices), controllers, state machines, door logic, hardware components, Discrete hardware or any other suitable circuitry or any combination of circuits that may carry out the various functionality described throughout this disclosure. Those skilled in the art will recognize the best way to implement the functionality described for the processing system depending on the particular application and the limitations of the overall design imposed on the overall system.

[0064] The machine readable media may comprise various software modules. Software modules include instructions that when executed by the processor cause the processing system to perform various functions. The software modules may include a transmission module and a reception module. Each software module can reside in a single storage device or can be distributed among multiple storage devices. As an example, a software module can be loaded into a RAM from a hard drive when an activation event occurs. During the execution of the software module, the processor can load part of the instructions in cache to increase the access speed. One or more cache lines can then be loaded into a general log file for execution by the processor. When reference is later made to the functionality of a software module, it should be understood that such functionality is implemented by the processor when executing instructions of that software module.

[0065] If implemented in software, the functions can be stored or transmitted as one or more instructions or code in a computer readable medium. The computer readable media includes both computer storage media and communication media, including any means that facilitates the transfer of a computer program from one location to another. A storage medium can be any available medium that can be accessed by a computer. By way of example, and not in a limiting manner, such computer-readable media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other means that it can be used to transport or store desired program code in the form of instructions or data structures and which can be accessed by a computer. In addition, any connection can be appropriately termed a computer readable medium. For example, if the software is transmitted from a website, a server or another remote source using a coaxial cable, a fiber optic cable, a twisted pair, a digital subscriber line (DSL) or wireless technologies such as infrared (IR ), radio and microwave, then coaxial cable, fiber optic cable, twisted pair, DSL or wireless technologies such as infrared, radio and microwave are included in the definition of medium. Discs, as used herein, include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray® discs, where discs typically reproduce data in a magnetic manner. as well as optically with laser. Therefore, in some aspects, computer readable media may comprise non-transient computer readable media (eg, tangible media). In addition, in other aspects, the computer readable media may comprise transient computer readable media (e.g., a signal). Combinations of the above should also be included within the scope of computer readable media.

[0066] Therefore, certain aspects may comprise a computer program product to carry carry out the operations presented in this document. For example, this computer program product may comprise a computer readable medium having instructions stored (and / or encoded) therein, where instructions may be executed by one or more processors to perform the operations described herein. document. In certain aspects, the computer program product may include packaging material.

[0067] Furthermore, it should be appreciated that the modules and / or other appropriate means for carrying out the methods and techniques described herein may be downloaded and / or otherwise obtained by a user terminal and / or a base station , as appropriate. For example, such a device may be coupled to a server to facilitate the transfer of means to carry out the procedures described herein. Alternatively, various methods described herein may be provided through storage means (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or a floppy disk, etc.), so that a user terminal and / or a base station can obtain the various methods after coupling or providing the storage means to the device. Any other suitable technique can also be used to provide the methods and techniques described herein to a device.

[0068] It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations can be made in the arrangement, operation and details of the methods and apparatuses described above without departing from the scope of the claims.

Claims (7)

i. A procedure for wireless communications, comprising: receiving, by a user terminal (120), a data packet comprising one or more data symbols; extracting, by the user terminal (120), a length field, LENGTH, and a correction field from the data packet, and calculating, by the user terminal (120) a number of data symbols, Nsym, in the packet, based on the length field using one of the expressions: N ^sym = ceil ((LENGTH + 3) / 3) - 4 - N ^vht - ^ltf ; N ^sym = soil ((ceil ((LENGTH + 3) / 3) - 4 - N ^vht - ^ltf ) * 4 / 3.6); Y N ^sym = soil ((ceil ((LENGTH + 3) / 3) - 4 - N ^vht - ^ltf ) * 4 / 3,6) - 1, where N ^vht - ^ltf is the number of Very High Performance Long Learning Fields and in which the expression is chosen based on the correction field. 2. The method of claim 1, wherein the ceiling function, ceil, maps a real number to the next smallest integral. 3. The method of claim 1, wherein the floor function maps a real number to the larger integral precedent. 4. A user terminal (120) for wireless communications, comprising: means for receiving a data packet comprising one or more data symbols; means to extract a length field, LENGTH, and a correction field from the data packet, and means for calculating a number of data symbols, Nsym, in the packet, based on the length field using one of the expressions: N ^sym = ceil ((LENGTH + 3) / 3) - 4 - N ^vht - ^ltf ; N ^sym = soil ((ceil ((LENGTH + 3) / 3) - 4 - N ^vht - ^ltf ) * 4 / 3.6); Y N ^sym = soil ((ceil ((LENGTH + 3) / 3) - 4 - N ^vht - ^ltf ) * 4 / 3,6) - 1, where N ^vht - ^ltf is the number of Very High Performance Long Learning Fields and in which the expression is chosen based on the correction field. 5. The user terminal (120) of claim 4, wherein the ceiling function, ceil, maps a real number to the next smallest integer. 6. The terminal (120) of claim 4, wherein the function floor, floor, maps a real number to the largest previous full. 7. A computer program product comprising a computer readable medium having instructions stored thereon, instructions executable by a processor to cause the processor to perform a method according to any of claims 1 to 3.